Setting and thermal expansion of a phosphate-bonded investment to titanium

Objectives: The aim of this investigation was to evaluate of the setting and thermal expansion of phosphate – bonded investment materials Rematitan Plus (RP), and Rema Exackt (RE) to determine in that temperature (until 600ºC), are suitable to compensate for the casting shrinkage of Ti. Methods: For measurement of the vertical setting expansion those investments were mixed with special liquid and invested into silicone molds of the metal pattern (50 mm x 10mm x 10mm). A glass plate and dial gauge were seated on the sample, after two hours was the measurement of the setting expansion (Se). The distance between ends (De) was measurement in a profile (Nikon) and the initial length (Li) of the sample was determined. The setting expansion (%) was calculated for: (Se/Li)x 100. For the thermal expansion, sample (50mm x 8mm) were positioned in the dilatometers (Netzsch Dil 402 PC) and heated at a rate of 5ºC/min to 800ºC and then cooled to 430ºC (T1), 515ºC (T2), 600ºC (T3) at the same rate. The casting shrinkage of titanium was estimated as 1,36%. The average of setting expansion was amounted with the thermal expansion. Results: The results were RP (T1) – 0,80%, RP (T2) – 0,90%, RP (T3) – 1,15%; RE (T1) – 1,13%, RE (T2) – 1,27%, RE (T3) – 1,55%. Conclusion: The material RP showed total expansion enough to compensate for the casting shrinkage of titanium in the research temperatures the investment RE in the temperatures T1 and T2 that showed values of expansion next to necessary.